The objective of this project is to continue the study of the genetics and biogeography of phlebotomine sand flies (Diptera: Psychodidae). Little is known about the genetics and the parameters that define the geographical boundaries of this important insect group, members of which serve as vectors of bartonellosis, a number of arboviral diseases and leishmaniasis. Studies will focus on field and laboratory studies of Lutzomyia longipalpis and L. shannoni, two sand fly species that have been implicated as vectors of leishmaniasis and have a very wide range of distribution in the Americas. Biochemical genetic profiles established for geographic strains of L. longipalpis, a species closely associated with human habitation, have identified distinctive populations that occur in regions of high endemic transmission or where unique clinical forms of visceral leishmaniasis have appeared. Characterization of these populations will take 3 forms: (1) a transect between genetically distinct populations will show the pattern of change in biochemical signature (abrupt or gradual), (2) infectivity and clinical progress by the parasite, Leishmania chagasi, in vertebrate host tissues will be compared among genetically/geographically defined strains of the vector, and (3) characterization of geographic parameters that are associated with the distribution of genetically distinctive vector populations. Lutzomyia shannoni is a forest species, a cryptic species complex, and a species associated with arrays of other sand flies across its geographic range. Its genotypic variability, the relationships among members of its species group, and clines of species associations will be characterized in selected areas. Collection, identification, establishing biochemical profiles and vector roles will involve the cooperative efforts of scientists at Yale University and the Instituto Nacional de Salud at Bogota, Colombia; in addition, sand fly specialists in the U.S. and Latin America, particularly in Brazil, Colombia, Panama and Costa Rica will assist in the collection of flies and field data.